In the web and film converting process, for example papermaking, the flat webs or films are heated by transporting them over and around one or more hollow metal cylinders. Such hollow cylinders are heated by steam and serve to perform the heating process during manufacturing. These cylinders are typically between four and seven feet in diameter. Steam is supplied to each cylinder through a rotary joint, thence through a roll journal, and thence into the interior of the cylinder. Inside the cylinder, the steam condenses as it transfers heat to the interior wall of the cylinder. The condensed steam or “condensate” must then be removed so that the cylinder does not fill with water. This condensate is removed through a syphon pipe, which, in turn, is connected to an external pipe or tank. Syphon pipes may rotate with the cylinder (“rotary” syphons) or remain fixed in relation to the rotary joint (“stationary” syphons). Stationary syphons that are used to remove condensate are attached to a stationary portion of the rotary joint to prevent the syphon from rotating with the cylinder.
In prior stationary syphon designs, the syphon pipe extends to and is positioned close to the inside surface of each heating cylinder. To improve the collection of condensate, a syphon shoe is connected to the end of the syphon pipe, and positioned adjacent to the inside surface of the cylinder. The syphon shoe is configured to collect the condensate, which is moving along the inner circumference of the cylinder. Generally, the syphon shoe is positioned close to the interior surface in order to prevent large amounts of condensate from accumulating inside the cylinder. The rotational velocity of the cylinder, and hence, the condensate, serves to force condensate into the syphon shoe.
At high operating speeds, a portion of the condensate that is collected inside the rotating cylinders will rotate with the cylinders in a condition termed “rimming”. For efficient operation at high operating speeds, the end of the stationary syphon that is facing the inside surface of the rotating cylinder is formed with an opening facing in the circumferential direction with an angled or contoured inner surface to scoop the rimming condensate from the inside surface of the rotating cylinder and re-direct it into the radial syphon pipe fluid passage and ultimately, out of the rotating cylinder. Typically, the pickup shoe affixed to the end of the syphon is provided with a single opening oriented circumferentially, which serves to perform the desired pickup of condensate, assuming that the cylinder, in operation, rotates in only a single direction. This configuration is taught by Partio in U.S. Pat. No. 5,335,427, Jenkner, et al., U.S. Pat. No. 4,501,075, and our U.S. Pat. No. 8,082,680. In some special applications, however, the cylinder may rotate in either a clockwise or counter-clockwise direction, depending on manufacturing requirements. In such applications, a stationary syphon shoe with its opening facing in the single circumferential direction will not adequately drain the condensate in the rotating cylinder when the cylinder is operating in the opposite direction.
For such applications, conventional stationary syphons are formed with an opening facing radially toward the inside surface of the rotating cylinder. This configuration allows the condensate to be removed from the rotating cylinder regardless of the direction of the rotation of the cylinder. Typical of this configuration is the device taught by Chance, et al., U.S. Pat. No. 4,384,412. However, in order for this configuration to function, the centrifugal force that tends to hold the condensate against the inside surface of the rotating cylinder must be overcome. This requires a high pressure difference between the pressure near the inside surface of the rotating cylinder and the pressure of the external pipe or tank where the condensate is exhausted from the syphon pipe. The high differential pressure is what entrains and lifts the condensate off the inside surface of the rotating cylinder and into the radial syphon pipe.
It is desirable, therefore, to provide a pickup shoe which performs the function of removing condensate from the interior of a rotating cylinder, regardless of the direction of rotation in said cylinder, without the need for high differential pressures and without allowing excessive amounts of steam to leave the rotating cylinder without condensing.